mdadm/test: add new testcase for testing readonly/readwrite

This is a test case for testing --readonly and
--readwrite feature, it covers common metadata
versions and raid levels.

Signed-off-by: Zhilong Liu <zlliu@suse.com>
Signed-off-by: Jes Sorensen <jsorensen@fb.com>

tests/00readonly

@@ -0,0 +1,22 @@
+#!/bin/bash
+
+for metadata in 0.9 1.0 1.1 1.2
+do
+	for level in linear raid0 raid1 raid4 raid5 raid6 raid10
+	do
+		mdadm -CR $md0 -l $level -n 4 --metadata=$metadata \
+			$dev1 $dev2 $dev3 $dev4 --assume-clean
+		check nosync
+		check $level
+		mdadm -ro $md0
+		check readonly
+		state=$(cat /sys/block/md0/md/array_state)
+		[ "$state" == "readonly" ] ||
+			die "array_state should be 'readonly', but is $state"
+		mdadm -w $md0
+		check $level
+		mdadm -S $md0
+	done
+done
+
+exit 0